I have a delema, for an upcoming brikwar I'm building.......buildings and I wondered if there are any floor building techneques
(I mean like second floor) I don't know about?
I have two basic ideas first there's just using plates of whatever size and putting them across the gap,
then I've used 2 x 4 bricks(it takes quite a few) but are there anymore options?
I've never owned any lego houses, how does Lego do it?
Any help would be appreciated.

I usually use combinations of plates of similar sizes, like 6byX, to cover the3 distance of a gap, usually between the wall of a building and two 1xLONG technic bricks in the middle, spanning the building. I might post some pictures later.

Often, literally, a pillow fight but may include similar situations like volleyball, particularly when wardrobe is skimpy and the action is bouncy.

I've built 6 story buildings for my Base. One of them is Grape Tower, which is sloppily held up by chains, dinosaur heads, thick columns, spit, and luck. That was how I built 4 years ago. Here is a technique that I use now:

Square first floor, usually 2 studs thick but it can be any thickness. Then either I put plates on the top if the building's small, or big thick plates if it's a big building. If you want extra stability, you can double or triple stack the plates, OR put cross beams from the top of one wall in the building to the opposite one. There are SO many different ways to build buildings. Here is a diagram: EDIT the diagram is messed up when it posts nevermind.

If you want really good in depth but easy building techniques and stuff you could get 'The Unofficial Lego Builder's Guide'. It's a great book, it has all kinds of awesome essential stuff in it.

lego started making these really cool massive single briks, that are about the size of standard plates, but as thick as briks. they make VERY easy quick buildings. but i'd go with blitzen's technique if you're looking for actually good construction quality.

Line the tops of all the walls with flat, studless plates that go all the way around the rim of the building. The ceiling should be the same width minus 1 brick all the way around and attached to the underside of the floor of the next story.

This technique allows you to easily take the building apart story by story so that you can access each one during a battle.